Incorporation of enzymes, particularly of proteinases into liquid detergent formulations has long been an objective of workers in the detergent arts. A particular difficulty that faced the art has been the rapid decrease of enzyme activity during storage of the liquid detergent product. To a substantial extent, the difficulty has been resolved by the art through inclusion of enzyme stabilizing ingredients such as lower alcohols, calcium ions, and organic acids. (See, for example, the teachings in U.S. Pat. Nos. 4,111,855 and 4,318,818.)
Successful stabilization of proteinase containing detergent formulations imposed upon the producers of the enzyme a requirement to supply enzyme in a form suited to use in the liquid formulations. Desirably, the enzyme supplier should provide a liquid enzyme concentrate adapted to the detergent formulation; indeed, the text of U.S. Pat. No. 4,318,818 appears to indicate that the stabilization system described therein is as applicable to liquid enzyme concentrates as to liquid detergent formulations.
However, the enzyme supplier must be concerned with storage stability of the enzyme concentrate as such, since significant delays can be encountered between preparation of the liquid enzyme concentrate by the enzyme supplier and delivery thereof to the detergent formulator. Both ezyme supplier and detergent formulator would be pleased if the liquid enzyme concentrate exhibited high enough stability to allow also for reasonable delay between delivery of the concentrate and dilution thereof into the detergent formulation without the need for cold storage.
Attention to stabilization of the enzyme concentrate is particularly important in the instance of Subtilisin Carlsberg, one industrial form of which is Alcalase.RTM.. Copending Patent Application Ser. No. 448,374, filed Dec. 9, 1982, now U.S. Pat. No. 4,497,897 relates to stabilizing this enzyme in 60-85% by weight propylene glycol, 10-35% water by certain levels of calcium ion and of C.sub.1 -C.sub.3 carboxylate ion. The same subject matter is briefly described in Research Disclosure May 1982, Number 277 at Page 170, #21751.
It has now been discovered that presence of certain NH.sub.2 substituted compounds stabilize Subtilisin Carlsberg.